1*4af43218SAnshuman Khandual.. SPDX-License-Identifier: GPL-2.0 2*4af43218SAnshuman Khandual 3*4af43218SAnshuman Khandual============================== 4*4af43218SAnshuman KhandualTrace Buffer Extension (TRBE). 5*4af43218SAnshuman Khandual============================== 6*4af43218SAnshuman Khandual 7*4af43218SAnshuman Khandual :Author: Anshuman Khandual <anshuman.khandual@arm.com> 8*4af43218SAnshuman Khandual :Date: November 2020 9*4af43218SAnshuman Khandual 10*4af43218SAnshuman KhandualHardware Description 11*4af43218SAnshuman Khandual-------------------- 12*4af43218SAnshuman Khandual 13*4af43218SAnshuman KhandualTrace Buffer Extension (TRBE) is a percpu hardware which captures in system 14*4af43218SAnshuman Khandualmemory, CPU traces generated from a corresponding percpu tracing unit. This 15*4af43218SAnshuman Khandualgets plugged in as a coresight sink device because the corresponding trace 16*4af43218SAnshuman Khandualgenerators (ETE), are plugged in as source device. 17*4af43218SAnshuman Khandual 18*4af43218SAnshuman KhandualThe TRBE is not compliant to CoreSight architecture specifications, but is 19*4af43218SAnshuman Khandualdriven via the CoreSight driver framework to support the ETE (which is 20*4af43218SAnshuman KhandualCoreSight compliant) integration. 21*4af43218SAnshuman Khandual 22*4af43218SAnshuman KhandualSysfs files and directories 23*4af43218SAnshuman Khandual--------------------------- 24*4af43218SAnshuman Khandual 25*4af43218SAnshuman KhandualThe TRBE devices appear on the existing coresight bus alongside the other 26*4af43218SAnshuman Khandualcoresight devices:: 27*4af43218SAnshuman Khandual 28*4af43218SAnshuman Khandual >$ ls /sys/bus/coresight/devices 29*4af43218SAnshuman Khandual trbe0 trbe1 trbe2 trbe3 30*4af43218SAnshuman Khandual 31*4af43218SAnshuman KhandualThe ``trbe<N>`` named TRBEs are associated with a CPU.:: 32*4af43218SAnshuman Khandual 33*4af43218SAnshuman Khandual >$ ls /sys/bus/coresight/devices/trbe0/ 34*4af43218SAnshuman Khandual align flag 35*4af43218SAnshuman Khandual 36*4af43218SAnshuman Khandual*Key file items are:-* 37*4af43218SAnshuman Khandual * ``align``: TRBE write pointer alignment 38*4af43218SAnshuman Khandual * ``flag``: TRBE updates memory with access and dirty flags 39